but at the end it's head pops off, starts flying around on it's own, and goes bonkers at you

Is that what that thing is supposed to be? I always figured it was just sort of hanging around or something.

And, now that I finally take a look at the achievement list, and see that it's named "Kyurionesu heddo", I feel a bit silly.

Yeah, I originally couldnt tell what in the hell it was, the thing is weird looking, and I'm most familiar with the game on Ultra mode, where, well... it's hard to even see the damn thing. Either way it makes just as much sense as the rest of that gigantic monster. Takes up the whole level, walks on molten rock, CONSTANTLY farts those super-irritating suicide bees at you (seriously, it never... stops.... doing that.... argh), shoots bullets from every conceivable part of it's body, and so on.

One thing I never could tell in that game though though wasnt that boss, but with the first boss. That very final pattern it does, what the hell *are* those things that are firing the bullet streams? They just sorta pop into existence and look like some sort of bizarre alien gate to another dimension, which makes even less sense due to the fact that there's like 6 of them; what the heck they have to do with that particular gigantic insect, I have no idea. It's hard to even get a good look at them at all, really.

That very final pattern it does, what the hell *are* those things that are firing the bullet streams?

If you watch it in slow motion, you can clearly see those things unfolding out of the bug's back, the part behind the broken bit. It's some sort of weird-ass organic cannon; nothing the game doesn't have in droves elsewhere...